**Core Concept**
Polycystic Ovary Syndrome (PCOS) is a complex endocrine disorder characterized by hyperandrogenism, ovulatory dysfunction, and polycystic ovaries on ultrasound. The underlying pathophysiology involves insulin resistance, ovarian stroma hyperplasia, and anovulation.

**Why the Correct Answer is Right**
The characteristic features of PCOS include hyperandrogenism, acne, hirsutism, and insulin resistance. These symptoms are due to excessive androgen production by the ovaries and adrenal glands. PCOS is also associated with an increased risk of metabolic syndrome, type 2 diabetes, and cardiovascular disease. The ovulatory dysfunction in PCOS leads to anovulatory cycles, resulting in irregular menstrual bleeding and infertility.

**Why Each Wrong Option is Incorrect**
**Option A:**
* This is incorrect because obesity is a common comorbidity in PCOS, particularly in women with insulin resistance.

**Option B:**
* This is incorrect because hypertension is a known complication of metabolic syndrome, which is associated with PCOS.

**Option C:**
* This is incorrect because thyroid dysfunction, particularly hypothyroidism, is a common finding in women with PCOS.

**Clinical Pearl / High-Yield Fact**
PCOS is a heterogeneous disorder, and its diagnosis is often based on clinical and ultrasound findings rather than a single laboratory test. A mnemonic to remember the classic features of PCOS is "HARM" - Hirsutism, Acne, Irregular Menses, and Obesity.

**Correct Answer: A. Obesity.**